I have made a pcb with DB25 connector for BOB and a print for stopping starting spindle. Software used GRBL1.1 and UGCS
this is how the nano is connected
Attachment 469362
Attachment 469364
the print with nano
Attachment 469366
Attachment 469368
connections BOB
Attachment 469370
schematic BOB (maybe some errors ??)
Attachment 469372
pcb start stop with relay
the start stop is in GRBL done with the pmw ( 0-10V) signal.
GRBL uses pin D11 for start/stop and rpm control.
the voltage have to be above 1 V to start the spindle. Just use S and M3 /M5
Attachment 469374
this is how the drivers are connected
Attachment 469376
Here I have to stop because I am on my limit for 8 files.